Back to the drawing board.
Existing FOB's weigh 24.5 grains. Our early prototype of a modified annular airfoil fletch was 23 grains but like everybody else we dislike weight on the rear end of the arrow so we took out weight in no-stress areas and got the weight down to a (calculated) 20 grains (the weight of 3 blazers with glue). We won't know for certain until we make a few and throw them on the scale. Here is what they will look like now.